ssh: rename from openssh, update nixos module name

Flake lock file updates:

• Updated input 'birdsong':
    'git+https://git.qenya.tel/qenya/birdsong?ref=main&rev=4e461f83a84aba32bdf640163375f1e31b699111' (2025-01-21)
  → 'git+https://git.qenya.tel/qenya/birdsong?ref=main&rev=007130e869f1223713d588ba0f125c586ca13623' (2025-02-04)

common/default.nix

@@ -8,10 +8,10 @@
     ./misc.nix
     ./nginx.nix
     ./nix.nix
-    ./openssh.nix
     ./packages.nix
     ./sanoid.nix
     ./security.nix
+    ./ssh.nix
     ./steam.nix
   ];
 }

common/ssh.nix

@@ -1,7 +1,7 @@
 { config, lib, pkgs, ... }:
 
 {
-  services.openssh = {
+  programs.ssh = {
     enable = true;
     settings = {
       PasswordAuthentication = false;

flake.lock

@@ -46,11 +46,11 @@
     },
     "birdsong": {
       "locked": {
-        "lastModified": 1737470105,
-        "narHash": "sha256-m5wsHkRDsilv6hVYL4BLWM+Gn8MsQwvxIvhC18FH7Lo=",
+        "lastModified": 1738699106,
+        "narHash": "sha256-pAe4pHn9OmVWBHdZOMQBO21mHnshOxQOaLu/mKycM6Q=",
         "ref": "main",
-        "rev": "4e461f83a84aba32bdf640163375f1e31b699111",
-        "revCount": 19,
+        "rev": "007130e869f1223713d588ba0f125c586ca13623",
+        "revCount": 20,
         "type": "git",
         "url": "https://git.qenya.tel/qenya/birdsong"
       },